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Working temperature: the working temperature of hard nitriding is generally between 480 ℃ and 550 ℃, and the common temperature is between 490 ℃ and 530 ℃.

 

 

 

Working principle: NH3 = n + 3 / 2h2

 

 

 

Among them, n is active nitrogen, which plays a role of nitriding.

 

 

 

Note: the life cycle of active nitrogen is very short. If it is not adsorbed by the workpiece, it will quickly combine to generate nitrogen and lose its activity. Nitrogen has no nitriding capacity.

 

 

 

Furnace atmosphere composition: NH3, N2, H2

 

 

 

Definition of nitrogen potential: kn = pnh3 / (pH2) 1.5 = [1 - (4 / 3) pH2] / (pH2) 1.5

 

 

 

Discrimination: the larger kn, the stronger nitriding capacity of atmosphere

 

 

 

Point of view: there is no strict correspondence between kn and nitrogen potential. If kn is high, the nitriding capacity may not be strong. For example, there are a lot of ammonia gas in the nitriding furnace, and few ammonia gas is cracked. Although kn is very high, there is less active nitrogen available in practice, and the nitriding capacity is not strong.

 

 

 

At the same kn, the atmosphere formed by the decomposition of pure ammonia is completely different from the atmosphere formed by the mixture of ammonia and cracked ammonia.